Photoflash lamp



Aug. 2, 1966 H. REIBER 3,263,457

PHOTOFLASH LAMP Filed Feb. 4, 1965 Hg@ Y@ 4.

lm/ervlof: Hans Reibe United States Patent O 4 Claims. (ci. 67-31) The present invention relates to a photoash lamp with radiation-transmitting bulb containing a filling of finely divided combustible material and a combustion-supporting gas, especially oxygen. Generally, these well known photofiash lamps are provided with current inleads sealed through the bulb and electrically connected to the ignition means which starts the combustion -in the lamp by means of an electrical impulse. In lamps of Ithe well known type such ignition means are located near to the center of the lbulb volume.

One of the most common type of photofiash lamps is one which has a bulb volume of about 4 cc. and is filled with 4 to 8 mg./cc. of shredded zirconium foil together with oxygen at a pressure of 1000 to 2000 mm. of Hg. A special type of such lamp has a filling of 20 mg. of zirconium foil and an oxygen pressure of 1325 mm. of Hg and supplies when flashed off a light quantity of 7500 lumen seconds (lm. sec.). The ignition means of this lamp consists of a primer 4which has -at its main constituents zirconium powder and an oxygen carrier. The primer is ignited by means of an ignition wire heated up by an electric current therethrough. The incandescent particles of the primer then `ignite the combustible mate* rial in the lamp. The ignition means, primer and ignition wire, are located near to `the center of the bulb volume and are supported by a mount, e.g. a glass bead mount sealed into the bulb.

There are also well known such photofiash lamps which have a bulb volume of only 1.2 cc. These small lamps have a proportionately higher density of filling material. Well known lamps of this size are filled with 18 mg./cc. of shredded zirconium foil, have an oxygen pressure of 5 atms. and produce a light quantity of about 7500 lm. sec. ln these lamps the ignition means is `also located near to the center of the bulb.

lt is an object of the present invention to attain la further diminution of the bulb of photofiash lamps. At first, however, it was not possible to obtain the desired light quantity of about 6000 to 8000 lm. sec. with an even smaller photofiash lamp. All experiments showed that there was a limit with bulb volumes of about l cc. `and below at which luminous intensity drops greatly. The luminous intensity of a photoflash lamp as used herein means that ratio light quantity/ oxygen quantity (lm. sec./ oxygen pressureXbulb volume). Luminous intensity may, however, also be defined as light quantity/mass of combustible material (1m. sec/mg. zirconium).

Experts explained the considerable dropping off of luminous intensity in photofiash lamps having a bulb volume of l cc. or less, in the high withdrawal of heat by the inner wall of the bulb adjacent t-o the combustible material. This explanation seems reasonable because in case of bulb diminuition the volume decreases quicker than the bulb surface and a bad surface effect is therefore noted with decreasing volume.

A tubular test lamp with 1.2 cc. bulb volume, 30 mg. of shredded zirconium foil and 6 atms. oxygen and with igniting means locate-d near t-o the center of the bulb volume had a light quantity of 7500 lm. sec. A d-iminution of the bulb volume to 0.5 cc. by lessening the tube cross-section produced, with equal filling quantity of zirconium and correspondingly increased oxygen pressure, a

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light quantity of only 3850 lm. sec. when the primer was located on current inleads 19 mm. long.

In the course of experiments with the ignition mechanism of photoflash lamps of different sizes there have been flashed off photoflash lamps by me-ans of so-called sympathetic ignition. For the sake of simplicity these test lamps had no own ignition means but consisted only of a closed bulb filled with zirconium foil and oxygen. It was :then observed that in this latter case, the previous measured drop in luminous intensity did not occur when the bulb volume was reduced below l cc. A photoash l-amp having a bulb volume of 0.5 cc. and being equal to the above mentioned one but not provided with ignition means produced a light quantity of 7100 lm. sec. The presence of the primer on 19 mm. long current inleads had, therefore brought about a decrease in light quantity by 46% down to 3850 lm. sec. A similar lamp with 9 mm. long current inleads showed a 30% decrease in light quantity, i.e, from 7100 down to 5000 lm. sec.

It follows from these unexpected test results that it is not the bulb wall but the ignition device which causes such a considera-ble dropping of luminous intensity in case of very small volume photoflash lamps.

With this knowledge a photoflash lamp with a bulb volume of less than l cc. and satisfactory luminous intensity was successfully produced comprising a bulb of radiation transmitting material filled with oxygen at a pressure exceeding 5 atms. and a finely divided com` bustible material, said bulb consisting of elongated, tubu- 'lar envelope having a volume which is smaller than 1 cc. The proportion of the internal diameter of the bulb to its length can be 0.5 but is preferably lower than 0.5 and lies between 0.2 and 0.4.

The reason for such a high luminous intensity is not yet clear. It may, however, be traced back to the special arrangement or design of the ignition means. In one of the embodiment-s the ignition means passing through the bulb Wall into the interior of the lamp is located as near as possible to one 0f the ends of the envelope. lt was not known hitherto that dropping of the luminous intensity with extreme diminution of the bulb volume may be prevented by such measures. The ignition means is located near to the bulb end so that the light quantity of the lamp which, of course, lis also dependent on the biulb size and on the kind and quantity of the filling material chosen, amounts at least to 5000 lm. sec. and is preferably 6000 to 8000 lm. sec. The combustion room must 4be as free as possible from current inleads or other ignition means or assemblies.

Test results have also shown that the size of the metallic surface of current inleads located in the lamp have some influence upon luminous intensity. By diminution of this surface luminous intensity has lalso been increased. An additional measure taken for the purpose of providing `a midget photoash lamp of high luminous intensity is to reduce the diameter of the current inleads to 0.15 mm. or less. Good results may also be obtained with a preferably non-metallic coating or lacquering of the current inleads which prevents oxidation or vaporization of the inleads.

These new lamps have, preferably, a bulb volume of 0.3 to 0.9 cc. and `are filled with 15 to 30 mg, (corresponding to 30 to 70 mg./ cc.) of shredded zirconium foil together with l0 to 20 atms. of oxygen. The desired light quantity of 6000 to 8000 lm. sec. is obtained if at least of the bulb volume is continuously or uninterruptedly free from ignition means. In the present tubular bulb that part of the bulb volume may be considered as being continuous which lies between two panallel planes which .are perpendicular to the lamp axis.

The present invention makes also possible an even further diminution of the bulb volume down to 0.1 cc.

and less. The filling pressure of these subminiature lamps amounts to some 100 atmospheres.

If manufacturing times are to be kept reasonably constant, about the same amount of oxygen will condense in the larger bulbs Ias in the smaller bulbs. As is apparent, when such bulbs warm up to room temperature, the smaller bulbs would therefore have higher internal pressures than the larger bulbs.

There have been tested tubular photofiash lamps with a bulb volume of 0.1 to 0.2 cc. The oxygen pressure in these lamps amounted to between 30 Iand 100 atms. and the filling of divided zirconium to 20 to 40 mg. The wall thickness of these bulbs can be between 0.5 to 1.5 mm. and is preferably about 1 mm. The diameter of the tubular envelope is 2 to 4 mm. and its length, 15 to 30 mm. The ratio of the inside diameter to the wall thickness is less than 8 and lies preferably between 2 and 5. The ratio of the length to the diameter of the inner bulb space is greater than 3 and lies preferably between 5 and 15.

Subminiature phototlash lamps according to the invention are manufactured in the following manner. The tubular envelope is dipped with its closed end into liquid nitrogen whereas the other still open end is in connection with the atmosphere. Thereupon, oxygen is slowly introduced through a small tube extended deep into the bulb and most of the oxygen condenses on the bottom of the bulb. Then, the bulb is closed by means of the glass bead carrying the ignition mount, which is put upon the bulb aperture and is sealed with the latter. In order to guarantee good fitting this glass bead is properly preshaped.

Further `advantages of the invention will be apparent from the following description and the accompanying drawings, wherein;

FIGS. 1 to 3 show photofiash lamps, the ignition means thereof consisting of primer, ignition wire, and a pair of current inleads.

FIGS. 4 and 5 show photofiash lamps which are ignited by means of a high-voltage or high-frequency spark.

FIG. 6 shows the filling of a subminiature photofiash lamp.

FIG. 7 shows the method of sealing a subminiature photoash lamp.

FIG. 8 shows a finished subminiature photofiash lamp in longitudinal section.

FIGS. 9 and 10 show two other sealing modifications.

The photoflash lamps shown in FIGS. 1-3 have a tubular elongated glass, i.e., vitreous, bulb 1 into which current inleads 2 and 3, respectively, are sealed. The current inlead interior ends are provided with primers 6 and are connected with each other through the ignition wire 7. Current inleads 2 and 3, primers 6, and ignition wire 7 together constitute the ignition means with the current inleads extending inwardly from an end of the envelope a distance of less than 25% of the total internal length of the envelope, and the portion of the envelope beyond the inward extent of the ignition means containing combustible material and constituting at least 75% of the total internal length of the envelope. This is shown in FIG. 2 by two planes E perpendicular to the lamp axis and including between them the bulb length and volume free from ignition means.

In FIGS. 2 and 3 the seal consists of a stem press 8 whereas in FIG. 1 the lamp was made from two parts between which the current inleads 2 .and 3 were put and which parts have been sealed together with their rims to form the seal 9.

In FIGS. 4 and 5 the current inleads 4 and 5, respectively, lare provided on their ends with spherical electrodes 10 and 11 between which a high voltage surge is applied producing a spark in the lamp which starts ignition. The current inleads 4 and 5 may be sealed in opposite ends of the bulb (FIG. or in the same end of the bulb (FIG. 4).

In these latter embodiments the ignition means consisting of current inleads and electrodes 10 and 11 are located so far back to one or both the ends of the bulb that the current inleads extend inwardly from at least one end of the envelope a total distance of less than 25% of the total internal length of the envelope, and the portion of the internal length of the envelope exclusive of the inward extents of the ignition means contains combustible material and constitutes at least 75% of the total internal length of the envelope. The lamps are provided inside an-d/ or outside with one or several protective coatings and may also be provided with .a colored filtering layer. The current inlead ends projecting beyond the lamp serve, preferably, as electrical contacts and the glass sections at the seal may serve as the base for inserting the lamp into a socket. There may be several lamps combined into a unit and they may, for instance, be embedded in a synthetic material so as to serve in a magazine flash device.

As isknown in the prior art, such as in Patents 2,768,- 517, Atkinson et al., and 2,811,846, Rively, single electrodes may be used for high-voltage ignition of photofiash lamps.

FIGS. 6 and 7 show a special method for the manufacture of very small photoash lamps. A pair of pincers 12 holds the bulb 14 having a closed end and an open end already filled with shredded zirconium foil 13 so that it extends with its lower closed end into liquid nitrogen 16. The upper open end, or aperture 15 of the bulb is somewhat enlarged conically. Oxygen is simultaneously introduced through a small tube 23 extending deep into the bulb, said tube having a diameter of about 0.6 mm. The oxygen is introduced with such a low speed that most of the oxygen 17 condenses on the bottom of the envelope. After la filling time of about 5 sec. a suicient quantity of oxygen is condensed and the ignition system 18 including the glass bead 19 is inserted into the conically enlarged bulb aperture 15. Thereupon, the glass bead 19 and bulb 14 are sealed together at the bulb aperture 15 by rotating them between very sharp gas-oxygen or oxyhydrogen ames. The bulb rim projects thereby beyond the glass bead by at least 1 mm.

FIG. 8 shows the shape of a finished photoflash lamp. The wall thickness of the lamp amounts to about 1 mm., the inside diameter of the tubular bulb is .about 2.5 mm. and the inner length of the tube is about 22 mm. The oxygen pressure at room temperature is 40,000 mm. of Hg tand the zirconium filling is 30 mg. The bulb volume is about 0.15 ce.

In the modification shown in FIG. 9, the glass bead 20 is located on a shoulder 21 of the bulb before it is sealed together with the bulb rim. In FIG. 10 the mount to be sealed-in is held by a second pair of pincers 22 so that the bulb need not be enlarged and glass bead and bulb do not come into contact before sealing. The above described filling method distinguishes from the methods known hitherto because the introduced gas condenses for the most part and the escaping part brings about a scavenging process. The gas filling is not sealed against the atmosphere but is in connection with it. Further, the greatly cooled envelope and the liquefied oxygen cool the ignition system located close to the seal so that no risk of flashing off exists when the sealing flames are applied.

Although the above-described methods of manufacturing photofiash lamps are not claimed herein, a divisional application `has been filed claiming such methods, Serial No. 535,621 filed December 16, 1965.

What I claim -as new and desire to secure by Letter Patent of the United States is:

1. A photoflash lamp comprising an elongated tubular envelope having a volume of less than one cubic centimeter and formed of radiation-transmitting vitreous material filled with oxygen at a pressure of about 20 atmospheres or greater, finely divided combustible material, and ignition means: said ignition means having at least one current inlead which extends inwardly from at least one end of said envelope a total distance of less than 25% of the total internal length of the envelope, and the portion of the internal length of the envelope exclusive of the inward extents of :the ignition means containing said combustible material and constituting at least 75% of the total internal length of the envelope.

2. A photoflash lamp according to claim 1 in which the pressure is between .approximately 30 and 100 atmosperes and the `bulb volume is between approximately 0.1 and 0.2 cubic centimeter.

3. A photollash lamp according to claim 1 in which the pressure is `at least about 100 atmospheres and the volume s less than about 0.1 cubic centimeter.

4. A photoflash lamp Iaccording to claim 1 in which the diameter of the current inlead is less than about 0.15 millimeter.

References Cited by the Examiner UNITED STATES PATENTS 2,325,667 8/1943 De Boer 67-31 2,794,699 6/1957 Eber S16-19 2,857,752 10/1958 Anderson et al 67-31 2,865,186 12/1958 Anderson et lal 67-31 2,879,634 `3/1959 Meyer 53-25 2,982,119 5/1961 Anderson 67-31 3,046,769 7/1962 Anderson et al 67-31 3,111,016 11/1963 Fink et al 67-31 FOREIGN PATENTS 589,531 12/ 1959 Canada.

FREDERICK L. MATTESON, IR., Primary Examiner. EDWARD J. MICHAEL, Examiner.

M. L. BATES, R. A. DUA, Assistant Examiners. 

1. A PHOTOFLASH LAMP COMPRISING AN ELONGATED TUBULAR ENVELOPE HAVING A VOLUME OF LESS THAN ONE CUBIC CENTIMETER AND FORMED OF RADIATION-TRANSMITTING VITREOUS MATERIAL FILLED WITH OXYGEN AT A PRESSURE OF ABOUT 20 ATMOSPHERES OR GREATER, FINELY DIVIDED COMBUSTIBLE MATERIAL, AND IGNITION MEANS: SAID IGNITION MEANS HAVING AT LEAST ONE CURRENT INLEAD WHICH EXTENDS INWARDLY FROM AT LEAST ONE END OF SAID ENVELOPE A TOTAL DISTANCE OF LESS THAN 25% OF THE TOTAL INTERNAL LENGTH OF THE ENVELOPE, AND THE PORTION OF THE INTERNAL LENGTH OF THE ENVELOPE EXCLUSIVE OF THE INWARD EXTENTS OF THE IGNITION MEANS CONTAINING SAID COMBUSTIBLE MATERIAL AND CONSTITUTING AT LEAST 75% OF THE TOTAL INTERNAL LENGTH OF THE ENVELOPE. 